The present invention relates to a programming device or system for a sewing machine capable of forming a succession of stitches or a stitch pattern or patterns on a workpiece under control of a batch of sewing instructions.
In the art of electronically-controlled sewing machines for industrial applications wherein a unit stitch pattern A as exemplified in FIG. 1 is formed in plural numbers as shown in FIG. 2 to provide a combination of the unit stitch patterns A (hereinafter referred to as "composite stitch pattern An) which are circumferentially disposed about a given point located at the center of formation, it has been a common practice in programming the composite stitch pattern An that sewing instructions for the stitch pattern An are prepared, with a cumbersome and time-consuming procedure, by tracing the profile of the pattern An while moving work holding means of the machine. More specifically, a prepared record medium on which the composite stitch pattern An is recorded is first retained on the work holding means. Then, the work holding means carrying the record medium is moved a stitch-to-stitch distance so that successive stitch positions of the pattern An on the rocord medium are sequentially brought into alignment with a needle position in the horizontal plane in order to prepare a sewing instruction for each of the stitches forming the composite pattern An. Thus, the sewing instructions necessary to create the composite stitch pattern An must be prepared by repeated movements of the work holding means to have the needle trace the pattern profile from one stitch to another for preparing the sewing instructions for all of the stitches.
As described above, the commonly practiced programming method or a device to practice the method in the art requires a lot of time and labor of the machine operator for preparing whole batch of sewing instructions, particularly where a desired stitch pattern includes a multiplicity of stitches like the composite stitch pattern An exemplified in FIG. 2. There exists a further shortcoming of such programming method and device that the stitch positions of the pattern An on the record medium must be exactly aligned with the needle position during preparation of the sewing instructions, otherwise a neat formation of the stitch pattern can not be obtained from the prepared sewing instructions.